1. Field of the Invention
The invention relates to a method for inspecting cameras mounted on vehicles such as an automobile, and systems for the same.
2. Description of the Related Art
Recent years, the spotlight has been centered on vehicle-driving monitoring systems using a monocular camera or a stereo camera as a preview sensor. Such a monitoring system uses a vehicle-mounted camera to image the views ahead of a vehicle and then executes an image recognition based on the imaged screen for the vehicle driving control such as in calling attention to the driver and in shifting to lower gear for deceleration.
Using the stereo camera as the preview sensor, pinpoint accuracy is needed for an installation position of the stereo camera to the vehicle as well as the quality of the stereo camera itself. The displacing of the installation position of the camera causes a shift of the imaging direction, resulting in deterioration in the reliability of the monitor control. Particularly, since in the stereo scheme, a distance is computed from parallax produced between a pair of imaged frames, the shift of the imaging direction directly exerts an influence upon the computed distance. Under present circumstances, however, the angle of individual vehicle-mounted camera is varied due to the limitations associated with deformation of the car body itself or the accuracy of installing the camera. In such shifting of the imaging direction, the image frames undergo an image transformation process, such as the affine transformation, to be finely adjusted with equivalence.
However, since a finely adjustable range by the image transformation is small in actual fact, the imaging directions of the vehicle-mounted camera may shift significantly from the range, resulting in the difficulties of the fine adjustment by the image transformation.
For this reason, it is needed to check whether or not the imaging directions of the installed camera fall within the correct range, through an inspection process performed after the camera is installed to the vehicle. If there are the cameras determined in the inspection process that the imaging directions sift from the correct range, they must undergo some mechanical re-adjustment, e.g. the re-installation of the camera, so that their imaging directions fall within the correct range. This requires a large-scale and expensive inspection apparatus and a lot of time and effort. There has been a desire to establish a test method for achieving efficiently the automation of such an inspection.
The present invention has been made in consideration of the aforementioned circumstances. It is therefore an object of the present invention to provide a method and a system for efficiently inspecting a vehicle-mounted camera, with eliminating the need for using a conventional inspection apparatus and with employing cooperation of an image processing unit and a vehicle-mounted navigation control unit to determine the camera quality through the inspections of an optical axis direction, a distance measurement accuracy and so on, i.e. whether or not they are in correct ranges, and then to display the determined results on a monitor of the vehicle-mounted navigation control unit for recommending adjustment.
To attain the object, a method for inspecting a vehicle-mounted camera according to the present invention is used for a vehicle monitoring system for imaging the view ahead of a vehicle with the camera installed to a vehicle body to recognize a running condition with an image processing unit, and includes the steps of inspecting the camera with the image processing unit to determine whether or not the camera quality is appropriate and displaying the inspected result on a monitor of a vehicle-mounted navigation control unit.
Further, the inspecting step for the quality assurance of the camera includes the steps of imaging an inspection chart, described with a reference pattern and placed at a predetermined position ahead of the vehicle, with the camera installed to the vehicle body, identifying a reference pattern on the camera image, and determining pass/fail of an optical axis direction of the camera on the basis of the relationship between a position of the identified reference pattern and a predetermined correct range defined for an imaging direction of the camera. In this event, the vehicle-mounted camera is attached through a replaceable attachment member to the vehicle body and has the imaging direction defined by a shape of the attachment member. Therefore, when the optical axis direction is determined to fail in the pass/fail determining step, another attachment member having a shape, optical axis direction by which is included in the correct range in the reference pattern of the recognized image, is selected from a plurality of pre-prepared attachment members of varying shapes. Replacement of the attachment member with the selected attachment member is recommended.
Furthermore, the inspecting step for the quality assurance of the camera includes the steps of imaging a plate described with a specific pattern and placed at a predetermined position ahead of the vehicle with the camera installed to the vehicle body, to calculate a distance image until the plate ahead of the vehicle with the image processing unit, and determining pass/fail of a distance measurement accuracy of the camera on a basis of comparison between the calculated distance image and a predetermined correct distance image characteristic.
Therefore, the present invention is for performing the inspection of at least the optical axis direction and the distance measurement accuracy for quality assurance of the vehicle-mounted camera to determine whether the camera quality is appropriate or not, and displaying the results on the monitor of the vehicle-mounted navigation control unit. For this reason, since the inspections for quality assurance relating to the visual check, the optical axis direction, the distance measurement accuracy and so on for the vehicle-mounted camera can be performed using the monitor of the vehicle-mounted navigation control unit, it is possible to eliminate the need for using any extra apparatus for the inspection processes, and also to reduce a working space for smoothly performing the inspections, resulting in significant efficiency of the inspection processes. Moreover, when the shifting of the imaging direction of the inspected camera is recognized, the information of the degree of shifting including the selection information for the replacement adjuster is provided to the operator for adjustment, resulting in efficiency of the re-adjusting process.
In addition, a system for inspecting a vehicle-mounted camera according to the present invention is used for a vehicle monitoring system for imaging the view ahead of a vehicle with a camera installed to the vehicle body to recognize a running condition with an image processing unit, and includes inspection means provided in the image processing unit for quality assurance of the camera and for determining whether the camera quality is appropriate or not, and display means of a vehicle-mounted navigation control unit for displaying the determined result. The image processing unit includes a recognition main unit and a quality inspection section as the inspection means, and the quality inspection section designates at least one of an optical axis direction and a distance measurement accuracy as inspection items to determine pass/fail of the designated measurement, and assigns information of selecting a displayed screen defined for each inspection item into a communication data so as to transmit it to the navigation control unit. Moreover, the system for inspecting the vehicle-mounted camera further includes switch means for starting the inspection means to execute the inspection for the quality assurance of the camera, and instructing the switching of a displayed screen defined for each inspection item.
According to the present invention, since the monitor for the vehicle-mounted navigation unit can be used to inspect for quality assurance relating to the visual check, the optical axis direction, the distance measurement accuracy and so on for the vehicle-mounted camera, any extra apparatus is not needed for the inspection processes but the inspection is smoothly performed in the reduced working space. This allows the significant efficiency of the inspection processes.
These and other objects and advantages of the present invention will become obvious to those skilled in the art upon review of the following description, the accompanying drawings and appended claims.